Thank-you for the confirmation that two later versions: 5.10.1 and 5.12.2 do not exhibit this behavior.

As to the "point" of posting the question? Well, for one, I wasn't 100% convinced the problem wasn't me. But even if I were, 5.10.0 is the system perl for an up-to-date Debian Lenny installation. As the newest Debian release (Sqeeze) was only a few weeks ago (Feb 6, 2011), there are still quite a lot of machines out there running Perl 5.10.0 and will be for some time.

System administrators are by and large a conservative bunch when it comes to the software running their operating system, so the advice "just upgrade" is usually lost on them. Debian moves slowly to release software updates because it wants to make sure all the different programs work together and it has the philosophy, as do many system administrators, that an old good-enough piece of software with a known bug is better than a shiny new piece of software that hasn't yet been tested for cross reactions with all of the other software on their system.

Additionally, reports and confirmation of bugs in legacy software can help push the decision to test and prepare for upgrade up the priority list.

Even when there isn't a potential to fix a bug via a patch or upgrade, I think it helps to know that there is a consensus that strange behavior X is in fact a bug. It allows people who have to work with that version of perl, to move on and focus on workarounds or alternatives rather than spending hours trying to fix something that can't be fixed (without a patch or upgrade).

In my case, this confirmation meant that I updated a test suite with a version check and added a caveat to some documentation. When I only had Corion's confirmation of a fix in 5.12, those caveats were for all versions before 5.12. Now, with your confirmation of good behavior on 5.10.1, I can lower the version threshold to 5.10.1

Thank-you again for taking the time to test this and report back on your results.